Per 6L6 wanting my question below to the statement above rerouted to an F5 thread (from the ACA thread)...
I'm thinking about an F5 build... and have bought a transformer—500VA—before reading this thread (so, not really thinking about it anymore I guess)...so I get that it's slightly overkill—but was in the range listed in the DIYStore info and price wasn't that Dif from the 400VA... I'm also confused by the PSU build—but I'll get into that on the PSU thread? Or can I wonder right here about what capacitors I need for that transformer (secondary voltage rating?) or is that even a relevant question? From reading this thread seems I'm not the only one with PSU related questions building an F5... and then there's this Dual Mono PS thing from the person quoted above... Could someone explain that? Like you are talking to a child? Haha. I know a lot about plumbing—not a lot about electricity—just enough to get myself into trouble.
So, what does Dual Mono PS look like, exactly, if I'm following the PSU build here on the forum (6L6) and building a single PSU, concurrent with the F5 build guide? the pictures I've seen show a single transformer connected to the PSU board and then to the respective amp boards. Is dual mono a power supply for each channel? So 2 PSUs? Also confused by the PSU build guide and the Discrete Diode Bridge part of the board—that seems to not be used in the F5 builds.... and I have yet to soloush what it does exactly anyway...
Not looking for complete answers on any of this—where's the fun in that?—and I'm still trying to read everything (and do my real work!) —one thing I know is that eventually I'll figure it out a piece at a time—it's just that I don't want to die trying. Thanks!
Basically, dual mono would mean you have a stereo amp, where each channel
gets its own fuse, transformer, rectifiers and PS board (assuming you're
using a PS board).
gets its own fuse, transformer, rectifiers and PS board (assuming you're
using a PS board).
Yep. What Dennis said.
One transformer, one PSU, one amp channel.
x2.
Yes, the chassis will get really packed. Yes, you can use a smaller transformer per side as it only needs to supply one channel at a time.
And when you're done thinking about it, you'll likely realize that it probably makes more sense to build monoblocks. 😀
pfarrell - check your PM
One transformer, one PSU, one amp channel.
x2.
Yes, the chassis will get really packed. Yes, you can use a smaller transformer per side as it only needs to supply one channel at a time.
And when you're done thinking about it, you'll likely realize that it probably makes more sense to build monoblocks. 😀
pfarrell - check your PM
Haha, well yes... so I had the right mental image... So... the most obvious question is... how is that not a mono block setup in a single chassis? Or is it? And what are the explicit advantages? That presumably I could hear?
I'm very blown away with the ACA, and the kit for the second one arrived today...So I'll be playing the mono block game—where are the boards for the B1 NuTube?????!!!!! Need that running too to keep the family happy with inputs besides a turntable. Haha..... Dualing F5s is crazy for my level right now. I'm gonna build one... and then go from there...
Hi. What is the power consumption of one of these boards.
I would have thought since class a is about 20% music and 80% heat, then for a 25watt amp it should be 125 watts per board. Does this sound about right. But the plan calls for 400va transformer.
Also, the plan advises a voltage of 18v up to 24v. What would happen with 18v? The amount of power the amp could produce will go down, but what is the effect on the sound quality.
Thanks!
I would have thought since class a is about 20% music and 80% heat, then for a 25watt amp it should be 125 watts per board. Does this sound about right. But the plan calls for 400va transformer.
Also, the plan advises a voltage of 18v up to 24v. What would happen with 18v? The amount of power the amp could produce will go down, but what is the effect on the sound quality.
Thanks!
Nelson recommends a 300VA transformer. Everybody grossly oversized the PSU because it’s easy and fun. 🙂
As for lower voltage, I’ve done a few experiments and yes, the max power is down but, in my opinion, the sound suffers a bit as well. This amp is very popular for a reason, (it sounds amazing) and it’s operating points were designed with 24v rails. I’d suggest keeping to that if you can.
As for lower voltage, I’ve done a few experiments and yes, the max power is down but, in my opinion, the sound suffers a bit as well. This amp is very popular for a reason, (it sounds amazing) and it’s operating points were designed with 24v rails. I’d suggest keeping to that if you can.
Thanks for the reply.
I thought that running the boards at a slightly lower voltage may help to keep them a little cooler and extend life, perhaps they are not pushed so hard and can cruise a little. Some class-a's die over the years from the amount of heat they put out.
I thought that running the boards at a slightly lower voltage may help to keep them a little cooler and extend life, perhaps they are not pushed so hard and can cruise a little. Some class-a's die over the years from the amount of heat they put out.
Or is it good heatsinking that is important.
Most amps have an input cap to block dc, is there a chance of dc upsetting this amp
Is my assumption of 125 watts power consumption per board accurate
Thanks!
Most amps have an input cap to block dc, is there a chance of dc upsetting this amp
Is my assumption of 125 watts power consumption per board accurate
Thanks!
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I too suggest keeping to approx 24V rails as designed. A good 300VA
transformer will do nicely but you can obviously go higher. (The commercial
F5 used a 300VA 2x18VAC Plitron.)
At 1.3A bias, each channel should draw less than 70W.
Good heatsinking, proper mounting/interface of the transistors and
a reasonable dissipation for each transistor should ensure a long service life.
transformer will do nicely but you can obviously go higher. (The commercial
F5 used a 300VA 2x18VAC Plitron.)
At 1.3A bias, each channel should draw less than 70W.
Good heatsinking, proper mounting/interface of the transistors and
a reasonable dissipation for each transistor should ensure a long service life.
Good Point.
Is it 70 watts for these particular boards? I thought it was 125. Even more confused now.
My suggestion is if the power consumption is 70 watt per board then a 200 va should be enough. Why should i spend extra money on a 400va, difficult to see any sonic benefits.
Is it 70 watts for these particular boards? I thought it was 125. Even more confused now.
My suggestion is if the power consumption is 70 watt per board then a 200 va should be enough. Why should i spend extra money on a 400va, difficult to see any sonic benefits.
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Transformer power in VA should be 6X the output power of the amplifier in W.
That’s the rule of thumb that Nelson uses. As I said, everybody likes to oversize the PSU because it seems like it’s a clear benefit. (It likely gains nothing, but that’s not going to stop anybody... 🙂 )
BUT, you not want to go much smaller than recommended because the transformer will be in a steady-state load and that’s what needs the extra capacity.
Tl;dr, 300VA is ideal. Smaller isn’t recommended, bigger makes the amplifier heavier.
That’s the rule of thumb that Nelson uses. As I said, everybody likes to oversize the PSU because it seems like it’s a clear benefit. (It likely gains nothing, but that’s not going to stop anybody... 🙂 )
BUT, you not want to go much smaller than recommended because the transformer will be in a steady-state load and that’s what needs the extra capacity.
Tl;dr, 300VA is ideal. Smaller isn’t recommended, bigger makes the amplifier heavier.
Sorry, not trying to be a nit picker, probably am being stupid, isn't 25 x 6 = 150
Dennis Hui, are you saying you modded the amp to get the power consumption down to 70 watts
Dennis Hui, are you saying you modded the amp to get the power consumption down to 70 watts
Oh right sorry my bad i thought you meant 300va per channel
So why is dennis hui saying less than 70 watts per channel
So why is dennis hui saying less than 70 watts per channel
The power draw is mostly coming from the output stage.
Standard bias on the output stage is 1.3A, running on +/-24V rails.
So that's about 2 x 1.3 * 24 ~63W for the output stage per channel.
Standard bias on the output stage is 1.3A, running on +/-24V rails.
So that's about 2 x 1.3 * 24 ~63W for the output stage per channel.
Thanks Dennis. With the fullest of reeespect to yourself, how is such a high efficiency possible. I thought class-a's were 80% heat and 20% music.
Is it something about the design of this amp
Is it something about the design of this amp
I think your 20% efficiency is a bit off. I've always heard class A falls in the 25% - 50% range.
Something like the Aleph or J2 might do even better as they have active current sources which follow the load to some extent.
Beyond that, is efficiency somewhat dependant on how close to the rails the amp can swing the output? Is the F5 reasonable good at this?
Something like the Aleph or J2 might do even better as they have active current sources which follow the load to some extent.
Beyond that, is efficiency somewhat dependant on how close to the rails the amp can swing the output? Is the F5 reasonable good at this?
Resistor
Hi,
I have one question, why original amp have 2,4ohm resitor with 0,47ohm resistor ?
Hi,
I have one question, why original amp have 2,4ohm resitor with 0,47ohm resistor ?
